The present invention relates generally to a printer in which printing is carried out on a recording medium through an ink ribbon which is withdrawn from and circulated into a ribbon cassette More particularly, the invention relates to a mechanism for detecting presence of a ribbon stopper used to tightly retain the ink ribbon in the cassette.
An ink ribbon cassette is typically used in dot impact printers, in which an endless loop ink ribbon is retained. For allowing the ribbon to be smoothly fed out from the cassette when printing is carried out, the ink ribbon is sinuously folded and loosely retained in the storage chamber of the ribbon cassette. If, in the ink ribbon loosely retained condition, the ribbon cassette is packed, shipped or distributed, the ink ribbon tends to be moved or turned over within the cassette, thereby causing a jam in the storage chamber. To avoid such a problem, the ink ribbon is held relatively tightly at one end of the storage chamber and is kept unmoved by a ribbon stopper located substantially at the center of the storage chamber. The ribbon stopper is not removed until the ink ribbon is actually used.
The ribbon stopper has to be removed when the ribbon cassette is mounted on a printer. However, since the users may not be aware of the existence of the ribbon stopper or otherwise not accustomed to the process of removing the ribbon stopper, they tend to forget to remove the ribbon stopper. If the printer is operated under the condition where the ribbon cassette is mounted on the printer without removing the ribbon stopper, the ink ribbon will be cut off when it is forcibly withdrawn, since the movement of the ink ribbon is bothered by the ribbon stopper. As a result, the ribbon cassette can no longer be used despite it is new.